WO2014196150A1 - Acousto-optic image pickup device - Google Patents

Abstract

An acousto-optic image pickup device disclosed in the present invention comprises the following: a drive unit that generates a drive signal formed by burst waves configured with a repetition of a plurality of reference waves; an ultrasonic wave source that receives the drive signal and outputs to the inside of an object ultrasonic waves which are in accordance with the drive signal; an acousto-optic medium section which has an acoustic opening and in which scattered ultrasonic waves generated as a result of the ultrasonic waves scattering inside of the object enter the acousto-optic medium from the acoustic opening and are propagated therein; a wedge light-source that emits a wedge beam of light of a single color that enters the acousto-optic medium section in a non-parallel direction with respect to the propagation direction of the scattered ultrasonic waves, where the light intensity of the wedge beam of light changes with the passing of time; an image forming optical system in which incident is diffraction light generated due to the wedge beam of light diffracting in the acousto-optic medium section according to a refraction index distribution generated in the acousto-optic medium section by the propagation of scattered ultrasonic waves, and in which an image is formed by converging the diffraction light; and an image pickup unit for picking up the image formed by the image forming optical system and outputting an electrical signal.

Description

Acousto-optic imaging device

The present application relates to an acoustooptic imaging apparatus, and more particularly to an acoustooptic imaging apparatus that acquires an ultrasonic echo obtained from an object as an optical image.

2. Description of the Related Art As an apparatus that irradiates an object with ultrasonic waves and generates an optical image using scattered waves from the object, an ultrasonic diagnostic apparatus as disclosed in Patent Document 1 is known. In an ultrasonic diagnostic apparatus, an ultrasonic wave is transmitted to and received from an object using a plurality of ultrasonic wave transmitting / receiving elements, and a received wave signal output from each element is delayed and synthesized to superimpose the object. A sound image is taken.

Such an ultrasonic diagnostic apparatus requires multiple signal processing (delay and synthesis) in order to capture one ultrasonic image. The number of necessary signal processing corresponds to at least the number of pixels of the image. Therefore, in order to image ultrasound at high speed, a signal processing circuit having a high-speed and large-scale arithmetic circuit is required. Further, in order to acquire an image with a large number of pixels and high spatial resolution, a large number of ultrasonic transducers having the same transmission / reception characteristics are required. However, it is extremely difficult to construct such a group of transducers.

JP-A-60-122549 International Publication No. 2012/172768

A non-limiting exemplary acousto-optic imaging device according to the present invention provides an acousto-optic imaging device capable of imaging the inside of an object without using a signal processing circuit with high calculation processing capability.

The acousto-optic imaging device disclosed in the present application generates a drive signal composed of burst waves generated by repetition of a plurality of reference waves, and receives the drive signal, and generates an ultrasonic wave corresponding to the drive signal inside the object. An ultrasonic source to output, an acoustic aperture, and scattered ultrasonic waves generated by scattering of the ultrasonic waves inside the object are incident from the acoustic aperture and propagated, A wedge light source that emits a wedge light flux that is incident on the acousto-optic medium section non-parallel to the propagating direction, and whose light intensity changes over time, and a scattered ultrasonic wave propagates An imaging optical system in which the wedge light flux is diffracted in the acousto-optic medium part by the refractive index distribution generated in the acousto-optic medium part, and the generated diffracted light is incident, and the diffracted light is focused. Comprising an imaging optical system for forming an image by Rukoto, taking an image formed by the imaging optical system and an imaging unit for outputting an electric signal.

According to the acousto-optic imaging device disclosed in the present application, the inside of an object can be photographed without using a signal processing circuit having a high processing capability. Further, even when ultrasonic wave propagation attenuation occurs in an object, it is possible to obtain optical images of portions located at different depths in the object with the same luminance.

It is a schematic diagram which shows the structure of 1st Embodiment of an acousto-optic imaging device. It is a figure which shows the flow of the signal in 1st Embodiment. (A) And (b) is a figure which shows the structure of the wedge light source in 1st Embodiment. It is a figure which shows another structure of the wedge light source in 1st Embodiment. (A) And (b) is a figure which shows another structure of the wedge light source in 1st Embodiment. It is a schematic diagram which shows another structure of 1st Embodiment. It is a figure explaining the flow of a signal of the acoustooptic imaging device of the structure of FIG. It is a figure which shows the simulation model of an acoustic propagation medium part. It is a figure which shows the calculation result of the diffracted light intensity in case the light intensity of a wedge light beam is constant. It is a figure which shows the time change of the light intensity of the light beam shown to Formula (6). (A) to (d) is a diagram showing a time waveform and timing of each part signal of the first embodiment. It is a figure which shows the calculation result of the diffracted light intensity in case the light intensity of a wedge light beam is shown by Formula (6). It is a figure which shows the calculation result of the diffracted light intensity in case the light intensity of a wedge light beam is shown by Formula (8). (A) And (b) is a schematic diagram which shows the mode of the image acquired in 1st Embodiment. It is a schematic diagram which shows the structure of 2nd Embodiment of an acousto-optic imaging device. It is a figure which shows the flow of the signal in 2nd Embodiment. (A) to (e) is a diagram showing a time waveform and timing of each part signal and exposure timing of the second embodiment. (A)-(e) is a figure which shows the time waveform and timing of another each part signal of 2nd Embodiment, and the timing of exposure. It is a schematic diagram which shows the structure of 3rd Embodiment of an acousto-optic imaging device. It is a figure which shows the flow of the signal in 3rd Embodiment. (A) to (e) is a diagram showing a time waveform and timing of each part signal and exposure timing of the third embodiment. (A) And (b) is a schematic diagram which shows the mode of the image acquired in 3rd Embodiment. (A) to (e) are diagrams showing another time waveform and timing of each part signal and exposure timing of the third embodiment. (A) And (b) is a schematic diagram which shows the mode of another image acquired in 3rd Embodiment. (A) to (e) are diagrams showing another time waveform and timing of each part signal and exposure timing of the third embodiment. (A) to (e) are diagrams showing another time waveform and timing of each part signal and exposure timing of the third embodiment. (A) to (e) are diagrams showing another time waveform and timing of each part signal and exposure timing of the third embodiment. It is a schematic diagram which shows the structure of 4th Embodiment of an acousto-optic imaging device. It is a figure which shows the flow of the signal in 4th Embodiment. (A)-(e) is a figure which shows the time waveform and timing of each part signal of 4th Embodiment, and the timing of exposure. (A)-(e) is a figure which shows another time waveform and timing of each part signal of 4th Embodiment, and the timing of exposure. It is a schematic diagram which shows the structure of 5th Embodiment of an acousto-optic imaging device.

The inventor of the present application examined a method of acquiring an image two-dimensionally or three-dimensionally, instead of obtaining an image by scanning an ultrasonic wave through a tissue inside a subject like a conventional ultrasonic diagnostic apparatus. . As a result, the inventors have conceived that an image of a tissue inside a subject is acquired using an acoustooptic effect that is an interaction between ultrasonic waves and light.

Specifically, A. Korpel, “Visualization of the cross section of a sound beam by Bragg diffraction of light," Applied Physics Letters, vol.9. No.12, pp.425-427,15 Dec. 1966. As disclosed in Non-Patent Document 1 below, acoustooptics are performed by irradiating an object with ultrasonic waves and propagating ultrasonic waves that are transmitted through the object or scattered from the object into the acoustooptic medium. If the refractive index distribution is formed in the medium and the intensity / phase distribution of transmitted or scattered ultrasonic waves is transferred to the intensity / phase distribution of monochromatic light using the Bragg diffraction generated thereby, the image inside the object is taken as an optical image. It is considered possible.

However, this Non-Patent Document 1 only discloses the acoustooptic effect by Bragg diffraction, and there is no suggestion how to realize imaging of a tissue in a living body by the acoustooptic effect.

The inventor of the present application has examined the technology disclosed in Non-Patent Document 1 in detail, and according to the configuration disclosed in Non-Patent Document 1, the frequency of ultrasonic waves used is as high as 15 MHz or higher. This is because the acousto-optic cell is composed of an aqueous medium, and the conditions under which Bragg diffraction occurs are limited by the relationship between the acoustic velocity of water (about 1500 m / s) and the wavelength of ultrasonic waves. . In a living body, absorption attenuation increases substantially in proportion to the frequency. Therefore, it is preferable to use an ultrasonic wave having a frequency of 10 MHz or less in order to image a deep interior of a subject. Therefore, even if the configuration disclosed in Non-Patent Document 1 is used as it is, it is difficult to obtain an image of the tissue in the body of the subject.

Further, according to the study of the present inventor, in the acousto-optic imaging device disclosed in Non-Patent Document 1, when ultrasonic waves are attenuated in an object, images of portions located at different depths in the object are different. It is considered that there is a problem that it is acquired with luminance.

The inventor of the present application has studied such a problem in detail and has come up with a novel acousto-optic imaging device. The outline of one aspect of the acousto-optic imaging device of the present invention is as follows.

An acoustooptic imaging device according to an embodiment of the present invention includes a drive unit that generates a drive signal composed of burst waves generated by repeating a plurality of reference waves, and an ultrasonic wave that receives the drive signal and that corresponds to the drive signal. An acousto-optic medium that has an ultrasonic source that outputs to the inside of the object and an acoustic aperture, and that the scattered ultrasonic waves generated by scattering of the ultrasonic wave inside the object enter the inside from the acoustic aperture and propagate A wedge light source that emits a wedge light beam that is incident on the acousto-optic medium unit non-parallel to a direction in which the scattered ultrasonic wave propagates, and whose light intensity changes over time; The wedge light flux is diffracted in the acoustooptic medium portion by the refractive index distribution generated in the acoustooptic medium portion due to the propagation of the scattered ultrasonic waves, and the generated circuit An imaging optical system in which light enters, an imaging optical system that forms an image by focusing the diffracted light, and an image that captures an image formed by the imaging optical system and outputs an electrical signal A part.

The acousto-optic imaging device may further include a trigger signal source that generates a trigger signal, and the drive unit may receive the trigger signal and generate the drive signal at a timing when the trigger signal is received.

The wedge light source receives the trigger signal, and continuously emits a wedge light beam at a timing when the trigger signal is received, and the light intensity of the wedge light beam increases within the predetermined time. Also good.

The imaging unit may receive the trigger signal, start exposure at a timing when the trigger signal is received, and continue exposure for an arbitrary time, and then stop the exposure.

The imaging unit may receive the trigger signal, start the exposure with an arbitrary time delay after receiving the trigger signal, continue the exposure for an arbitrary time, and then stop the exposure.

The trigger signal source repeatedly generates the trigger signal a plurality of times, and each time the trigger signal is generated, the drive unit, the ultrasonic source, and the wedge light source repeatedly operate, and the imaging unit Each time the trigger signal is received, after the trigger signal is received, exposure is started at an arbitrary time delay, exposure is continued for an arbitrary time, exposure is stopped, and the wedge light source is repeatedly operated. Among the plurality of wedge light beams to be generated, the light intensities of two wedge light beams corresponding to at least two of the plurality of trigger signals may be different from each other.

The acousto-optic imaging device further includes a trigger signal source that generates a trigger signal, and a delay generator that receives the trigger signal and generates a delayed trigger signal with a predetermined time delay, and the wedge light source includes the delayed trigger signal When the delay trigger signal is received, a wedge light beam is continuously emitted for a predetermined time, and the drive unit receives the delay trigger signal and receives the trigger signal at the timing when the trigger signal is received. The imaging unit may receive the trigger signal, start exposure at a timing when the trigger signal is received, and continue exposure for an arbitrary time, and then stop exposure.

The imaging unit may be configured such that the time for which the exposure is continued can be changed.

The acousto-optic imaging device further includes a detector that detects a part of the wedge light beam that has passed through the acousto-optic medium unit and outputs a detection signal. The trigger signal source refers to the detection signal, and the next trigger signal May be generated.

The wedge light source includes a laser light source that emits a monochromatic light beam, an enlargement optical system that receives the monochromatic light beam from the light source and emits an enlarged plane wave light beam, and a plane wave light beam emitted from the enlargement optical system. The cylindrical lens has a refractive power for focusing in the first direction on a plane perpendicular to the propagation direction of the incident plane wave light beam, and the second direction perpendicular to the first direction. The first lens lens may have no refractive power, and the first direction of the cylindrical lens may be parallel to the direction in which the scattered ultrasound propagates.

The wedge light source may include a light intensity modulation signal source that generates a light intensity modulation signal, and a laser diode that emits the luminous flux of the monochromatic light having a light intensity corresponding to the light intensity modulation signal.

The wedge light source may further include an optical modulator that modulates the light intensity of the monochromatic light beam emitted from the laser light source, the plane wave beam emitted from the magnifying optical system, or the plane wave beam emitted from the cylindrical lens. Good.

The optical modulator may receive a modulation signal and modulate the light intensity of the monochromatic light beam or plane wave light beam in accordance with the modulation signal.

The optical modulator includes a rotating disk provided with a neutral density filter having a distribution in which light attenuation factors differ in a circumferential direction, and a motor that rotates the rotating disk, and the rotating disk is a luminous flux of the monochromatic light. Alternatively, a plane wave light beam is disposed so as to pass through the neutral density filter, and with the rotation of the rotating disk, the attenuation factor of the light of the neutral density filter through which the monochromatic light beam or plane wave light beam is transmitted is different. The light intensity of the wedge luminous flux may be changed.

The time change of the light intensity of the wedge luminous flux may be represented by a simple increase function.

The simple increase function may be an exponential function.

The simple increase function may be a power function or a function composed of a sum of power functions.

The number of reference waves in the burst wave may be 10 or more and 1000 or less.

The trigger signal source repeatedly generates the trigger signal, and the driving unit, the ultrasonic source, the wedge light source, and the imaging unit each repeatedly operate each time the trigger signal is generated, The predetermined time during which the emission of the plurality of wedge light beams generated by repeatedly operating the wedge light source may be different from each other in at least two of the plurality of wedge light beams.

The trigger signal source repeatedly generates the trigger signal, and the driving unit, the ultrasonic source, the wedge light source, and the imaging unit each repeatedly operate each time the trigger signal is generated, The duration of exposure in a plurality of exposures caused by repeated operation of the imaging unit may be different from each other in at least two of the plurality of exposures.

The trigger signal source repeatedly generates the trigger signal, and the driving unit, the ultrasonic source, the wedge light source, and the imaging unit each repeatedly operate each time the trigger signal is generated, The delay time until the start of exposure in a plurality of exposures due to repeated operation of the imaging unit may be different from each other in at least two of the plurality of exposures.

The trigger signal source repeatedly generates the trigger signal a plurality of times, and the delay generator, the drive unit, the ultrasonic source, the wedge light source, and the imaging unit repeat each time the trigger signal is generated. The delay time until the start of signal output in the plurality of delay trigger signals generated by repeatedly operating the delay generator may be different from each other in at least two of the plurality of delay trigger signals. .

The time for which the exposure in the imaging unit is continued may be substantially equal to the time for which the burst wave of the drive signal continues.

The wedge light source is based on a delay time until exposure starts in the exposure of the imaging unit and a time during which exposure continues, and light in the two wedge light fluxes corresponding to at least two of the plurality of trigger signals. The intensity may be determined.

The acousto-optic imaging device reflects the wedge light beam emitted from the wedge light source so as to be incident on the acousto-optic medium unit, and reflects the diffracted light generated in the acousto-optic medium unit to reflect the imaging optical system. And an exit-side mirror that enters the light source.

An acousto-optic imaging device according to another aspect of the present invention includes a trigger signal source that generates a trigger signal, and a burst wave generated by repeating a plurality of reference waves at a timing at which the trigger signal is received and the trigger signal is received. A drive unit configured to generate a drive signal, an ultrasonic source that receives the drive signal and outputs an ultrasonic wave corresponding to the drive signal to the inside of the object, and an acoustic aperture, and the ultrasonic wave is the object Scattered ultrasonic waves generated by scattering inside are incident on the inside of the acoustic aperture and propagated to the acoustooptic medium part non-parallel to the propagation direction of the scattered ultrasonic waves The acoustic wave is generated by a wedge light source that emits a monochromatic wedge light beam that is incident, and a refractive index distribution generated in the acousto-optic medium unit by the propagation of the scattered ultrasonic waves. An imaging optical system in which the wedge light beam is diffracted in the academic medium portion and the generated diffracted light is incident, and an imaging optical system that forms an image by focusing the diffracted light, and the imaging optical system The trigger signal source includes: an imaging unit that captures the formed image and outputs an electrical signal; and a signal processing unit that receives the electrical signal from the imaging unit and adjusts the brightness of the captured image. A plurality of trigger signals are repeatedly generated, and each time the trigger signal is generated, the drive unit, the ultrasonic source, the wedge light source, and the imaging unit repeatedly operate, and the signal processing unit The brightness of at least two images is adjusted so that the average brightness of at least two images is constant among a plurality of captured images generated by the imaging unit repeatedly operating. That.

<Embodiment 1>
Hereinafter, a first embodiment of an acousto-optic imaging device of the present invention will be described. FIG. 1 is a schematic configuration diagram of an acousto-optic imaging device 100 according to the first embodiment.

(Configuration of acousto-optic imaging device 100)
The acousto-optic imaging device 100 includes a wedge light source 1, an acousto-optic medium unit 2, an imaging optical system 3, an imaging unit 4, an ultrasonic source 5, a driving unit 51, and a trigger signal source 6. Hereinafter, as shown in FIG. 1, the propagation direction (optical axis) of the wedge luminous flux 9 is defined as the z axis, and the direction perpendicular to the acoustic aperture 203 that is the surface where the object 7 and the acoustooptic medium portion 2 are in contact is defined as the y axis. In the following description, the direction perpendicular to the paper plane, which is the direction perpendicular to the y-axis and the z-axis, is defined as the x-axis.

The trigger signal source 6 is electrically connected to the wedge light source 1 and the drive unit 51, and the trigger signal output from the trigger signal source 6 is input to the wedge light source 1 and the drive unit 51. The ultrasonic source 5 is electrically connected to the drive unit 51, and a drive signal output from the drive unit 51 is input to the ultrasonic source 5.

The ultrasonic source 5 is arranged so as to be in contact with the object 7 at the time of photographing, and outputs the ultrasonic wave 8 inside the object 7. The ultrasonic wave 8 propagates through the object 7, and if there is a part with different acoustic characteristics (impedance) in the object 7, scattered ultrasonic waves are generated in that part. For example, FIG. 1 shows a state where the parts 7a and 7b exist in the object 7, and scattered ultrasonic waves 8a and 8b are generated in the parts 7a and 7b.

The acoustooptic medium unit 2 is disposed so as to be in contact with the object 7 through the acoustic aperture 203 at the time of imaging, and takes in the scattered ultrasonic waves 8 a and 8 b generated in the object 7. The scattered ultrasonic waves 8 a and 8 b generated in the object 7 are taken into the acousto-optic medium unit 2, and the scattered ultrasonic waves 8 a and 8 b having information on the object 7 in intensity and phase distribution propagate in the acousto-optic medium 201. .

The wedge light source 1 emits a wedge light beam 9 toward the acousto-optic medium unit 2. The wedge light beam 9 converges in the y direction (first direction) in FIG. 1 to have a focal point, and propagates in parallel without converging in the x direction (second direction). Further, the focal point of the wedge light beam 9 is located on the opposite side of the wedge light source 1 with the acoustooptic medium unit 2 interposed therebetween, that is, between the acoustooptic medium unit 2 and the imaging optical system 3. Further, the light intensity of the wedge luminous flux 9 changes with time.

When the scattered ultrasonic waves 8a and 8b propagate through the acoustooptic medium 201, the scattered ultrasonic waves 8a and 8b are sparse and dense waves (longitudinal waves), so that a sparse and dense distribution is generated in the acoustooptic medium 201. This sparse / dense distribution functions as a diffraction grating for the wedge light beam 9, and a −1st order diffracted light beam 9a, a 0th order diffracted light beam 9b, and a + 1st order diffracted light beam 9c are generated. The −1st order diffracted light beam 9a and the + 1st order diffracted light beam 9c are focused on the focal plane 10a to form an image of the object 7. Here, the focal plane 10a refers to a plane (xy plane) that passes through the focus of the wedge beam 9 and is perpendicular to the propagation direction of the wedge beam 9.

The image formed on the focal plane 10a is incomplete and forms an image in the direction in which the wedge beam 9 is converged (y direction), but in the direction in which the wedge beam 9 is propagated in parallel (x direction). The image is not formed. The imaging optical system 3 is disposed at a position facing the wedge light source 1 with the acousto-optic medium unit 2 interposed therebetween. The −1st order diffracted light beam 9a and the + 1st order diffracted light beam 9c that have passed through the acoustooptic medium unit 2 enter the imaging optical system 3, and are also focused in the x direction by the imaging optical system 3 to form an image. That is, the incomplete image of the object 7 formed by the −1st order diffracted light beam 9a and the + 1st order diffracted light beam 9c is formed as a complete image by the image forming optical system 3 on the image forming surface 10b. The imaging unit 4 captures an image of the −1st order diffracted light beam 9a or + 1st order diffracted light beam 9c formed by the imaging optical system 3, and converts the image into an electrical signal.

FIG. 2 schematically shows the main components of the acousto-optic imaging device 100 and the signal flow thereof. The operation of the acousto-optic imaging device will be briefly described with reference to FIG.

First, the trigger signal generated by the trigger signal source 6 is input to the drive unit 51 and the wedge light source 1. The drive unit 51 receives the trigger signal and generates a drive signal at the received timing. The ultrasonic source 5 receives a driving signal from the driving unit 51 and generates an ultrasonic wave corresponding to the driving signal. The generated ultrasonic wave enters the object 7, and the scattered ultrasonic wave generated by the object 7 enters the acoustooptic medium unit 2. Here, “received timing” means a time immediately after receiving a trigger signal without providing an intended delay time in the acousto-optic imaging device, and substantially means simultaneous. However, it may not be strictly the same, and there may be a delay of about the time required for signal processing and the like that inevitably occur in the acousto-optic imaging device.

The wedge light source 1 receives the trigger signal and emits the wedge light beam 9 for a predetermined time at the received timing. The light intensity of the wedge luminous flux 9 increases within a predetermined time based on the input time of the trigger signal.

The scattered ultrasonic waves and the wedge light beam 9 are incident on the acoustooptic medium unit 2 and come into contact with each other, whereby a diffraction image corresponding to the object 7 is generated. When the imaging unit 4 captures the generated diffraction image, a diffraction image corresponding to the object 7 can be acquired. In this way, the acoustooptic imaging device 100 acquires an image of the object 7 via the ultrasonic wave 8. The trigger signal source 6 repeatedly generates the trigger signal a plurality of times, and each time the trigger signal is received, the drive unit 51, the wedge light source 1 and the imaging unit 4 perform the above-described operation. Hereinafter, each component will be described in detail.

(Trigger signal source 6)
The trigger signal source 6 repeats the trigger signal and outputs it to the drive unit 51 and the wedge light source 1. The trigger signal may be a single pulse signal or a continuous signal that periodically outputs pulses. The time at which the trigger signal is generated is indicated by t ₀ to t _N or the like. That is, the time when the Nth trigger signal is generated is indicated by t _N.

(Wedge light source 1)
The wedge light source 1 emits a wedge light beam 9 of monochromatic light. In this embodiment, the wedge light source 1 emits the wedge light beam 9 for a predetermined time at the timing of receiving the trigger signal every time the trigger signal is received. The wedge beam 9 is focused on the focal plane 10a in the yz plane as shown in FIG. 3A, and is not propagated in parallel in the xz plane as shown in FIG. 3B. Since the wedge light beam 9 propagates in the z direction, it can be said that it converges in the y direction (first direction) and does not converge in the x direction (second direction). The position of the focal plane 10a of the wedge luminous flux 9 is opposite to the wedge light source 1 with the acoustooptic medium section 2 interposed therebetween, that is, between the acoustooptic medium section 2 and the imaging optical system 3 (FIG. 1). To position. The light intensity of the wedge luminous flux 9 changes with time according to a predetermined light intensity function with reference to the time when the trigger signal is received. More specifically, within a predetermined time, the light intensity of the wedge luminous flux increases as time elapses from the reference time. After emitting the wedge luminous flux 9 whose light intensity increases according to a predetermined light intensity function for a predetermined time, the wedge light source 1 ends the emission and waits until the next trigger signal is input. The predetermined time when the wedge light beam 9 is emitted is equal to or shorter than the repetition period of the trigger signal. Here, the time change of the light intensity means that the light intensity in the state where the wedge light beam 9 is emitted changes with time, and the light intensity depending on the state where the wedge light beam 9 is not emitted and the state where it is emitted. Does not include changes.

The function indicating the temporal change in the light intensity of the wedge luminous flux 9 may be a simple increase function. For example, it may be an exponential function, a power function, or a function composed of the sum of a plurality of power functions.

For the above-described functions, the wedge light source 1 includes a laser light source 11, an enlargement optical system 12, an optical aperture 13, a cylindrical lens 14, and a light intensity modulation signal source 15 as shown in FIG.

As shown in FIG. 3, the light intensity modulation signal source 15 receives a trigger signal and outputs a light intensity modulation signal whose voltage or current varies and increases according to a predetermined light intensity function at the timing of receiving the trigger signal. The light intensity modulation signal source 15 is electrically connected to the laser light source 11, and the laser light source 11 receives the light intensity modulation signal. The laser light source 11 emits a monochromatic light beam 91 having a light intensity corresponding to the voltage or current of the light intensity modulation signal. A monochromatic light beam 91 emitted from the laser light source 11 enters the magnifying optical system 12. The magnifying optical system 12 expands the aperture of the monochromatic light beam 91 emitted from the laser light source 11 and emits a plane wave beam 92 having an expanded aperture. The plane wave light beam 92 passes through the optical aperture 13 and enters the cylindrical lens 14.

The cylindrical lens 14 is set so that the plane wave light beam 92 is focused on the focal plane 10a after passing through the acoustooptic medium unit 2 in the y direction. The plane wave light beam 92 having no refractive power in the x direction and passing through the magnifying optical system 12 passes through the acoustooptic medium unit 2 as a parallel light beam, and does not form an image on the focal plane 10a.

In the configuration shown in FIG. 3, in order to obtain a monochromatic light beam 91 having a light intensity corresponding to the light intensity modulation signal, a laser diode (LD) is used as the laser light source 11 and the current is modulated in the light intensity modulation signal source 15. If the generated light intensity modulation signal is generated and used as a drive current source, the LD can be directly modulated.

The wedge light source 1 may have a configuration other than the configuration shown in FIG. For example, as shown in FIG. 4, the wedge light source 1 ′ further includes a light modulator 16, and based on the light intensity modulation signal, a constant light intensity regardless of the time when the light modulator 16 emits from the laser light source 11. You may modulate the light intensity of the light beam 91 which has. As shown in FIG. 4, a monochromatic light beam 91 emitted from the laser light source 11 enters the optical modulator 16. The light modulator 16 receives the light intensity modulation signal from the light intensity modulation signal source 15 and modulates the light intensity of the light beam 91 according to the voltage or current magnitude of the light intensity modulation signal. The monochromatic light beam 91 emitted from the light modulator 16 passes through the magnifying optical system 12, the optical aperture 13, and the cylindrical lens 14 and becomes a wedge light beam 9 as described with reference to FIG. 3. The light modulator 16 may further modulate the light intensity of the light beam 91 so as to block the light beam 91. Thereby, the optical modulator 16 can also realize a standby state in which the wedge light beam 9 is not emitted from the wedge light source 1.

According to the configuration shown in FIG. 4, it is not always necessary to use an LD as the laser light source 11, and there is no restriction on the type of the laser light source. For example, a gas laser such as a He—Ne laser can be used.

As the optical modulator 16, an optical modulator (EOM) using an electro-optic effect such as a commercially available optical modulator (AOM: Acoustic-Optical Modulator), an LN modulator (LiNbO ₃ ), or the like. Electro-Optical Modulator), optical modulator using electro-optical absorption effect (EA modulator: Electro-Absorption), etc., as well as using optical modulators using magneto-optic effect, thermo-optic effect, nonlinear optical effect, etc. Is possible.

If the trigger signal is a continuous pulse signal, the wedge light source 1 ″ may include an optical modulator 16 ′ including a neutral density filter instead of the above-described configuration. As shown in FIGS. 5 (a) and 5 (b), the optical modulator 16 ′ rotates the rotating disk 17a provided with a neutral density filter having a distribution in which the attenuation factor of light differs in the circulation direction, and the rotating disk 17a. Including a motor 17b.

The motor 17b rotates at the same period as the repetition period of the trigger signal by the light intensity modulation signal output from the light intensity modulation signal source 15. The temporal change of the light intensity can be adjusted by the distribution of the attenuation factor of the neutral density filter applied to the rotating disk 17a. The rotating disk 17a is arranged so that the light beam 91 passes through the neutral density filter, and the light intensity changes as the rotational disk 17a rotates and the attenuation factor of the neutral density filter at the position where the luminous flux 91 is incident changes. To do. Thereby, the intensity change of the light intensity can be obtained in a cycle in which the rotating disk 17a rotates once. The rotating disk 17a may further include a light shielding plate portion that substantially blocks the light beam 91 at the end of the neutral density filter. Thereby, the optical modulator 16 ′ can also realize a standby state in which the wedge light beam 9 is not emitted from the wedge light source 1.

In the configuration shown in FIG. 5, when it is difficult to make the trigger signal period coincide with the rotation period of the rotary disk 17a, the control shown in FIG. 6 may be used.

Specifically, as shown in FIG. 6, the acousto-optic imaging device 100 ′ may further include a photoelectric conversion element 18 that detects a part of the wedge light beam 9. For example, the photoelectric conversion element 18 detects a 0th-order diffracted light beam 9b which is a part of the wedge light beam 9 on the imaging surface 10b, and outputs a detection signal corresponding to the detected light intensity.

The trigger signal source 6 has a storage unit that stores a predetermined threshold value. The trigger signal source 6 receives the detection signal of the photoelectric conversion element 18 and outputs a pulse signal as a trigger signal at a timing when the detection signal changes from a state larger than a threshold value to a smaller state.

FIG. 7 schematically shows the main components of the acousto-optic imaging device 100 ′ having the configuration shown in FIG. 6 and the signal flow thereof. As shown in FIG. 7, first, the wedge light beam 9 enters the acousto-optic medium unit 2 from the wedge light source 1 ″. The photoelectric conversion element 18 receives the 0th-order diffracted light beam 9b emitted from the acoustooptic medium unit 2, performs photoelectric conversion, and generates a detection signal. The trigger signal source 6 receives the detection signal generated by the photoelectric conversion element 18 and generates a trigger signal at the timing described above. The trigger signal source 6 outputs the generated trigger signal to the drive unit 51 and the wedge light source 1. The drive unit 51 receives the trigger signal, generates a drive signal at the received timing, and outputs the drive signal to the ultrasonic source 5. The ultrasonic source 5 generates an ultrasonic wave by a drive signal and transmits the ultrasonic wave toward the object 7. Scattered ultrasonic waves generated by the object 7 enter the acoustooptic medium unit 2.

The wedge light source 1 ″ emits the wedge light beam 9 toward the acousto-optic medium unit 2. As described above, the light intensity of the wedge luminous flux 9 changes with the passage of time at the timing when the trigger signal is received, and changes according to a predetermined light intensity function for a predetermined time. Thereafter, the output of the wedge luminous flux 9 is terminated, and the process waits until the next trigger signal is input. In the acousto-optic medium unit 2, scattered ultrasonic waves and wedge light beams 9 enter and come into contact with each other, thereby generating a diffraction image corresponding to the object 7. When the generated diffraction image enters the imaging unit 4, a diffraction image corresponding to the object 7 is obtained. As described above, the acoustooptic imaging device 100 ′ illustrated in FIGS. 5 and 6 acquires an image of the object 7 via the ultrasonic wave 8. Note that the configuration of FIG. 6 is applicable to cases other than the case where the optical modulator 16 having the rotating disk 17a is used.

With the configuration as described above, the wedge light source 1 ″ emits the monochromatic light wedge light flux 9 whose light intensity changes with respect to the trigger signal toward the acoustooptic medium unit 2.

(Driver 51)
In this embodiment, the drive unit 51 generates and outputs a drive signal at the timing of receiving the trigger signal every time the trigger signal is received from the trigger signal source 6. After generating the drive signal, the drive unit 51 waits until the next trigger signal is input.

The drive signal output by the drive unit 51 is a burst wave generated by repeating a plurality of identical reference waveforms. For example, the drive signal is a sine wave having a time waveform in which a sine waveform having a constant amplitude and frequency is continuous for a fixed time. The reference waveform may be a rectangular wave or a triangular wave.

When the wave number of the sine wave is large and the duration of the drive signal is long, the duration of the transmitted ultrasonic wave is also long, and the ultrasonic waves scattered at different parts in the object 7 at different depths are timed. Separation becomes difficult. For this reason, it is preferable to determine the wave number of the sine wave so that the length of the ultrasonic wave is less than or equal to the depth of the region to be observed in the object 7. For example, consider a case where the object 7 is a living body and a 10 MHz burst sine wave is input as a drive signal. A living body is substantially equivalent to water, and the sound velocity of ultrasonic waves in water is approximately 1500 m / sec. Therefore, the wavelength of a 10 MHz sine wave is 0.15 mm. The length of the burst ultrasonic wave in water by the burst-like sine wave signal of wave number 10 is 1.5 mm, and the length of the burst ultrasonic wave in the water by the burst-like sine wave signal of wave number 100 is 15 mm. For example, when observing in a depth region of about 100 mm in the object 7, if the wave number is about 100 or less, the length of the burst ultrasonic wave becomes sufficiently shorter than the depth of the observation region. When observing in a depth region of about 10 mm, if a burst ultrasonic wave of about 10 waves is used, the length of the burst ultrasonic wave is sufficiently shorter than the depth of the observation region.

Although it is preferable that the wave number of the reference waveform in the drive signal is small, if the wave number is small, the duration time of the ultrasonic wave is also small, so that the generation time of the diffraction image is shortened and the exposure amount of the diffraction image is small. In this case, the exposure amount can be increased by increasing the repetition frequency of the trigger signal and increasing the number of exposures. For the reason described above, when the wave number of the reference waveform is about 10 or more and 1000 or less, the object 7 can be photographed with an appropriate exposure amount and resolution in the depth direction.

(Ultrasonic source 5)
The ultrasonic source 5 is disposed in contact with the object 7 during imaging. The ultrasonic source 5 is driven each time it receives a drive signal from the drive unit 51 and transmits an ultrasonic wave 8. The ultrasonic wave 8 is transmitted substantially uniformly over the area of the object 7 to be photographed. The ultrasonic wave 8 incident on the object 7 by the ultrasonic source 5 may be a plane wave or may not be a plane wave. The adhesion between the ultrasonic source 5 and the object 7 may be improved by using an alignment material such as an ultrasonic gel so that the ultrasonic source 5 can efficiently enter the ultrasonic wave 8 on the object 7.

(Object 7)
The object 7 is made of a material whose ultrasonic wave propagation attenuation is not extremely large. An example of the object 7 is a living body, and another example is a liquid such as water. When the object 7 is a living body, the internal portions 7a and 7b of the object 7 may be tissues such as blood vessels and organs in the living body.

(Ultrasonic 8)
The ultrasonic wave 8 incident on the object 7 propagates through the object 7. When there are portions 7a and 7b having different acoustic characteristics from the substance constituting the object 7, when the ultrasonic waves 8 are irradiated on the portions 7a and 7b, scattered ultrasonic waves 8a and 8b having the same frequency as the ultrasonic waves 8 are applied. Produces. The scattered ultrasonic waves enter the acoustooptic medium unit 2 from the acoustoscopic aperture 203 and propagate through the acoustooptic medium unit 2. At this time, since the propagation distance of the ultrasonic wave 8 and the propagation distance of the scattered ultrasonic wave become larger as the part is located deeper, the intensity of the scattered ultrasonic waves 8a and 8b is weak, and the time delays acoustooptics. Incident on the medium portion 2. The scattered ultrasonic waves 8a and 8b incident on the inside of the acousto-optic medium unit 2 have intensity and phase distribution reflecting the internal structure of the object 7 (difference in acoustic characteristics).

For example, let us consider a case where the portions 7a and 7b having different acoustic characteristics from the substance constituting the object 7 are located at different depths in the object 7 as shown in FIG. When the ultrasonic waves 8 are applied to the portions 7a and 7b, scattered ultrasonic waves 8a and 8b having the same frequency as the ultrasonic waves 8 are generated. The scattered ultrasonic waves 8 a and 8 b are incident on the inside of the acoustooptic medium unit 2 through the acoustic aperture 203. At this time, the scattered ultrasonic wave 8b of the portion 7b located at a deeper position in the object 7 is compared with the scattered ultrasonic wave 8a of the portion 7a located at a shallower position. The propagation distance until the ultrasonic wave 8 reaches each of the parts 7a and 7b from the ultrasonic source 5 is larger in the part 7b than in the part 7a. Further, the distance until the scattered ultrasonic waves 8a and 8b generated in the portions 7a and 7b reach the acoustooptic medium unit 2 is larger in the scattered ultrasonic wave 8b from the portion 7b than in the scattered ultrasonic wave 8a from the portion 7a. large. Therefore, the scattered ultrasonic wave 8b reaches the inside of the acoustooptic medium unit 2 later than the scattered ultrasonic wave 8a. Further, the propagation attenuation in the object 7 is larger in the scattered ultrasonic wave 8b than in the scattered ultrasonic wave 8a.

(Acousto-optic medium part 2)
The acoustooptic medium unit 2 includes an acoustooptic medium 201 and a cell 202, and the acoustooptic medium 201 is included in the cell 202. The acousto-optic medium unit 2 is disposed so as to be in contact with the object 7 at the acoustic aperture 203 when the object 7 is photographed. By arranging the acoustic aperture 203 in contact with the object 7, scattered ultrasonic waves 8 a and 8 b from the object 7 reaching the acoustic aperture 203 are taken into the acoustooptic medium unit 2. As described above, in order to efficiently propagate the scattered ultrasonic waves 8 a and 8 b into the acoustooptic medium unit 2, a matching material such as an ultrasonic gel is disposed between the object 7 and the acoustooptic medium unit 2, A matching layer may be disposed.

The scattered ultrasonic waves 8a and 8b propagate in the y-axis direction in FIG. This direction is perpendicular to the surface constituting the acoustic aperture 203 and is the normal direction of the acoustic aperture 203 when the scattered ultrasonic wave 8a is incident on the acoustic aperture 203 perpendicularly.

Since the scattered ultrasonic waves 8a and 8b are longitudinal waves, when the scattered ultrasonic waves 8a and 8b propagate through the acoustooptic medium 201, the sound pressure distribution of the acoustooptic medium 201, that is, the wave front of the scattered ultrasonic waves 8a and 8b coincides. A refractive index distribution is generated in the acousto-optic medium 201. At a certain moment, the refractive index distribution generated in the acousto-optic medium 201 becomes a sinusoidal diffraction grating that is repeated at the wavelength of the ultrasonic wave.

When the wedge light beam 9 is incident non-parallel to the propagation direction of the scattered ultrasonic waves 8a and 8b, the wedge light beam 9 is diffracted by the diffraction grating formed by the refractive index distribution in the acoustooptic medium 201, and a diffracted light beam is generated. . In FIG. 1, only the −1st order diffracted light beam 9a, the 0th order diffracted light beam 9b, and the + 1st order diffracted light beam 9c are shown for simplicity. In general, diffracted light includes Bragg diffracted light and Raman-Nath diffracted light. In the Bragg region where Klein Cook's parameter Q satisfies Q >> 1, Bragg diffracted light is the main diffracted light. In this case, the diffracted light to be generated is only the −1st order diffracted light beam 9a, the 0th order diffracted light beam 9b, and the + 1st order diffracted light beam 9c. For this reason, if it is operated in the Bragg region, the acousto-optic imaging device of the present embodiment can observe the inside of the object with high sensitivity. At this time, the brightness of the diffracted light is proportional to the amount of change in the refractive index of the diffraction grating, that is, the sound pressure of the ultrasonic waves. The Klein Cook parameter Q can be expressed by the following equation.

Here, L represents the interaction length between the ultrasonic wave and the light wave, λ represents the wavelength of the light wave, f represents the frequency of the ultrasonic wave, n represents the refractive index, and V represents the speed of sound. However, the acousto-optic imaging device of the present embodiment may be operated under a diffraction condition mainly including Raman-Nath diffracted light.

The scattered ultrasonic waves 8 a and 8 b continue to propagate through the acousto-optic medium unit 2 even after contacting the wedge light beam 9. However, if the light is reflected at the end of the acousto-optic medium unit 2 and again comes into contact with the wedge light beam 9, there is a possibility that the acquisition of the image is hindered. For this reason, a sound wave absorption end 204 may be provided at the end of the acoustooptic medium unit 2 opposite to the acoustic aperture 203 to suppress reflection of the scattered ultrasonic waves 8a and 8b.

The cell 202 and the acoustooptic medium 201 are made of a material that is transparent with respect to the wavelength of the light wave output from the laser light source 10 so that the wedge light beam 9 can be incident thereon. For example, a glass cell can be used as the cell 202.

Note that the cells 202 do not necessarily have to be made of a transparent material, and may be made of a material that is not transparent except for the portion where the wedge light flux 9 enters and exits. For example, the acoustic opening 203 constituting the cell 202 may be a material that is not transparent.

As the acousto-optic medium 201, water transparent to the wavelength of the light wave output from the laser light source 10, a fluorine-based liquid material, a silica nanoporous material, or the like can be used. When a high-resolution image is acquired by the acousto-optic imaging device 100, it is preferable to use a medium with the lowest possible sound velocity as the acousto-optic medium 201. In particular, when the object is a living body, it is preferable to use an ultrasonic wave having a frequency of 10 MHz or less in order to suppress attenuation due to absorption of the ultrasonic wave propagating through the object. In this case, since Bragg diffraction occurs, it is preferable to use a medium having a lower sound velocity than water. More specifically, it is preferable to use a fluorinated liquid material. For example, the speed of sound of water is 1500 m / sec, whereas the speed of sound of NovecTM 7200 (hydrofluoroether) manufactured by Sumitomo 3M Limited is 630 m / sec. Fluorine-based liquid materials such as Novec ™ 7000, Novec ™ 7100, Novec ™ 7200, Novec ™ 7300, Fluorinert TMFC-72 and FC-3283 are also materials having a low sound velocity. Further, the sound speed of the silica nanoporous material is as low as 50 to 250 m / sec, which is a preferable material for use as the acoustooptic medium 201.

( Diffraction beam 9a, 9c)
The −1st order diffracted light beam 9a and the + 1st order diffracted light beam 9c generated by the action of the scattered ultrasonic wave having the information of the object 7 and the wedge light beam 9 in the acoustooptic medium 201 pass through the focus of the wedge light beam 9 and An image is formed in the y direction on the focal plane 10a, which is a plane perpendicular to the propagation direction, and an optical image of the object 7 is generated on the focal plane 10a. However, the optical image of the object 7 generated at this time is an incomplete optical image that is not formed in the x direction.

The -1st order diffracted light beam 9a and the + 1st order diffracted light beam 9c generated by the action of the scattered ultrasonic waves 8a and 8b having information inside the object 7 and the wedge light beam 9 in the acoustooptic medium 201 have the focus of the wedge light beam 9 At the focal plane 10a that is positioned and perpendicular to the propagation direction of the wedge light beam, it converges in the y direction and forms an optical image of the object 7. However, the optical image of the object 7 generated at this time does not form an image in the x direction. As will be described in detail below, an optical image of the object 7 in the xz plane is generated on the focal plane 10a in a state where no image is formed in the x direction.

(Imaging optical system 3)
The −1st order diffracted light beam 9 a and the + 1st order diffracted light beam 9 c transmitted through the acoustooptic medium unit 2 enter the imaging optical system 3. The −1st order diffracted light beam 9a and the + 1st order diffracted light beam 9c pass through the imaging optical system 3, thereby forming an image in the x direction (second direction), and the x direction and the y direction on the imaging surface 10b. A complete optical image forming an image in either direction is generated.

The imaging optical system 3 includes, for example, a cylindrical lens 3a and a cylindrical lens 3b as shown in FIG. The cylindrical lens 3a is arranged so as to have a refractive power in the y direction and no refractive power in the x direction. The cylindrical lens 3b is arranged so as to have a refractive power in the x direction and no refractive power in the y direction.

Similarly, the 0th-order diffracted light beam 9b that has passed through the focal plane 10a is converged in the y direction by the cylindrical lens 3a of the imaging optical system 3, and is focused in the y direction on the imaging plane 10b. Further, the light is converged in the x direction by the cylindrical lens 3b and focused on the image plane 10b.

(Imaging unit 4)
The imaging unit 4 takes an optical image by the −1st order diffracted light beam 9a or the + 1st order diffracted light beam 9c on the imaging surface 10b, and converts it into an electrical signal. Thereby, the information inside the object 7 can be detected by ultrasonic waves and acquired as an optical image. The exposure time of the imaging unit 4 is set sufficiently longer than the repetition period of the trigger signal.

The light-shielding unit 21 may block the 0th-order diffracted light beam 9b or the other diffracted light beam that is not received so that only the −1st-order diffracted light beam 9a or the + 1st-order diffracted light beam 9c is incident on the imaging unit 4.

The imaging unit 4 includes, for example, a solid-state imaging device such as a CCD element or a CMOS element, detects the light intensity distribution of the diffracted image by the −1st order diffracted light beam 9a or the + 1st order diffracted light beam 9c as an optical image, and outputs an electrical signal. Convert to In the present embodiment, the exposure time of the imaging unit 4 is sufficiently longer than the repetition period of the trigger signal source 6.

Next, an optical image obtained by the acoustooptic imaging device 100 of the present embodiment will be described with reference to specific examples.

In the following embodiments, the object 7 is a living body, and a burst signal having a wave number of 10 at 10 MHz is input to the ultrasonic source 5 from the drive unit 51. A rectangular parallelepiped cell made of Tempax glass is used as the cell 202 of the acoustooptic medium unit 2, and the thickness of the glass constituting the cell is 1.1 mm. The inside of the cell 202 is filled with a Novec ™ 7200 having an acoustic velocity V = 630 m / s as an acousto-optic medium 201. Tempax glass and Novec ™ 7200 are translucent to He—Ne laser light having a wavelength of 633 nm, which will be described later. As the laser light source 11, a He—Ne laser having a wavelength of 633 nm is used. When a He—Ne laser having a wavelength of 633 nm is used, first-order Bragg diffracted light is generated at a diffraction angle of 0.28 ° by a diffraction grating in the acousto-optic medium 201 generated by an ultrasonic wave of 10 MHz.

Hereinafter, with reference to FIG. 8, it is simulated how the brightness of the image changes depending on which depth the object 7 is positioned in. In FIG. 8, the ultrasonic wave 8 is incident from the ultrasonic wave source 5 on the object 7 where the portion 71 exists at the position of the depth d. The incident ultrasonic wave propagates through the object 7 and reaches the portion 71, and is reflected and scattered by the portion 71 to generate a scattered ultrasonic wave 81. The generated scattered ultrasound 81 reaches the acoustooptic medium unit 2, enters the acoustooptic medium 201 through the acoustic aperture 203, and propagates through the acoustooptic medium 201 as a dense wave 82. The dense wave 82 in the acousto-optic medium 201 contacts the wedge light beam 9. The dense wave 82 having the information of the portion 71 in the object 7 in amplitude and phase acts on the wedge light beam 9 to be diffracted, thereby diffracting by the + 1st order diffracted light beam 9c at the diffraction angle θ _B = 0.28 °. An image is generated. For simplicity, the incident ultrasonic wave is a plane wave, the portion 71 is parallel to the acoustic aperture 203 and is sufficiently large and uniform, and totally reflects the touched ultrasonic wave. Sound attenuation is not considered.

In the above model, since the portion 71 is uniform in the xz plane, a diffraction image with uniform intensity is obtained. When the depth d where the portion 71 is located changes, it is calculated how the light intensity of the obtained image changes due to attenuation of the ultrasonic wave in the object 7. In the following, α = 3 dB / cm at 10 MHz is assumed as the ultrasonic attenuation constant in the living body.

A method of calculating the light intensity distribution of the −1st order diffracted light beam 9a or the + 1st order diffracted light beam 9c generated when the wedge light beam 9 comes into contact with the dense wave 82 will be described. For the sake of simplicity, as shown in FIG. 8, the wedge light beam 9 is treated as a collection of n light beams that pass through the focal point on the focal plane 10a. The diffracted image generated when the dense wave 82 and the wedge light beam 9 come into contact with each other in the acousto-optic medium 201 is a sum of diffracted light beams generated by diffracting each light beam by the dense wave 82. 8, each light beam z-coordinate is diffracted by z _0, z _m, scattered perpendicular plane leave the z-axis is z _e ultrasound 8b is a point on the z 'axis on the respective focal plane 10a It shows how an image is formed by z ₀ ′, z _m ′, and z _e ′. The z ′ axis is parallel to and opposite to the y axis. The image formed on the focal plane 10a is an incomplete image that forms an image in the y direction but does not form an image in the x direction. This image is converged in the x direction by the imaging optical system 3 to form an image of the object 7 on the imaging surface 10b. The light intensity distribution in the y direction of the image on the imaging surface 10b is determined by the light intensity distribution in the y direction of the image of the −1st order diffracted light beam 9a or the + 1st order diffracted light beam 9c on the focal plane 10a. In order to examine the light intensity distribution, the light intensity distribution of the image on the focal plane 10a may be examined.

First, consider a case where the wedge luminous flux 9 has a uniform intensity without changing over time. Each diffracted light intensity I _k is shown in Formula (1).

The sound pressure P of the dense wave 82 that reciprocally propagates through the acousto-optic medium 201 having the propagation attenuation factor α by a depth d is expressed as shown in Equation (2).

Here, P ₀ indicates the sound pressure of the dense wave 82 in the acoustooptic medium 201 when α = 0.

The light intensity I _image of the diffracted image on the focal plane 10a is expressed by the following equation (3).

Here, J ₁ represents the first-order Bessel function, Δn represents the amount of change in the refractive index caused by the sound pressure of 1 Pa, and λ represents the wavelength of the wedge luminous flux 9. The sound pressure P ₀ can be changed according to the intensity of the ultrasonic wave 8 incident from the ultrasonic source 5. Here, for the sake of simplicity, consider the case (P ₀ = λ / (2πΔn)) given by equation (4).

FIG. 9 shows the calculation result when α = −34.5 Np / m (−3 dB / cm) and the number of light rays n of the wedge luminous flux 9 = 100. As shown in FIG. 9, a change occurs in the light intensity of the image on the focal plane 10a due to propagation attenuation of the ultrasonic wave. It can be confirmed that the diffracted image of the object at a deeper position has a weaker light intensity and becomes weaker at d = 5 cm until it becomes about 0.1% in the case of d = 0 cm. This indicates that the light intensity of the image obtained by the imaging unit 4 varies greatly depending on the depth d. For example, when an imaging device having only a dynamic range of about 25 dB is used as the imaging unit 4, an object at a depth of 0 cm and an object at a depth of 5 cm have different light intensities of about 30 dB, so that images can be taken simultaneously. It suggests that you can't. In addition, the vertical axis | shaft of FIG. 9 is normalized with the light intensity of the diffraction image in d = 0.

The time t ′ from when the ultrasonic wave is emitted from the ultrasonic source 5, reflected by the portion 71 located at the depth d, and incident on the acoustooptic medium unit 2 is the sound speed V (= 1500 m / sec) of the living body. Thus, it can be expressed by equation (5).

Assuming that Δt is the time from when the dense wave enters the acousto-optic medium unit 2 until it comes into contact with the wedge light beam 9, the time from when the ultrasonic wave is emitted at time 0 until the dense wave 82 comes into contact with the wedge light beam is It can be expressed as t ′ + Δt. Δt is constant, but t ′ varies with the depth d. That is, the time during which the dense wave 82 from the part where the depth d is different starts to come into contact with the wedge light flux 9 differs depending on the depth d, and when the duration of the dense wave 82 is sufficiently short, these can be separated in time. Is possible. By utilizing this, the change in the light intensity of the image is corrected by giving a time change to the light intensity of the wedge light beam 9.

Consider a case in which the light intensity changes as a function of the light intensity of the wedge luminous flux 9 by an exponential function of time represented by Expression (6).

Here, the light intensity function I may be 0 in the time of 0 ≦ t ≦ Δt, or may be as shown in Equation (6).

FIG. 10 shows the change over time of the light intensity of the wedge luminous flux 9 when Δt = 0 in the equation (6).

FIG. 11 shows the operation timing of each part of the acoustooptic imaging device when the ultrasonic wave reflected by the portion 71 having the depth d is incident on the acoustooptic medium 201 and the dense wave 82 is in contact with the wedge light beam 9. ing. FIG. 11A shows a trigger signal from the trigger signal source 6. FIG. 11 (b) shows the light intensity of the wedge beam 9, which change with time in equation (6) based on the time t ₀ when the trigger signal is input. Wedge light source 1, the repetition period shorter than the time within T _w of the trigger signal according to equation (6), and outputs the wedge beam 9 where the light intensity changes, stops the subsequent output is then input the next trigger signal Wait until FIG. 11C shows the sound pressure of the ultrasonic wave incident from the ultrasonic wave source 5, and an ultrasonic wave that continues for 10 waves is input at a frequency of 10 MHz from the time t ₀ when the trigger signal is input. Yes. FIG. 11D shows a time waveform of sound pressure at a position where the incident ultrasonic wave is reflected by the portion 71 having the depth d and is in contact with the wedge light beam 9 of the dense wave 82 propagating through the acoustooptic medium portion 2. Yes. As shown in FIG. 11 (d), when the portion 71 is at a different depth d, the time during which the dense wave 82 contacts the wedge light beam 9 is changed.

The time for which the dense wave 82 due to the scattered ultrasonic waves from the portion 71 located at the depth d is in contact with the wedge light beam 9 is approximately determined by the equation (5). Therefore, when this is substituted into the equation (6), the equation (7) It becomes like this.

FIG. 12 shows the calculation result using Equation (7). From FIG. 12, the amount of change in the light intensity of the diffraction image with respect to the depth d of the portion 71 is smaller than in FIG. 9, and it can be confirmed that a substantially constant light intensity is obtained at a depth of 2 cm or more. . Note that the light intensity of the diffracted image with respect to the portion 71 having a depth of 2 cm or less is substantially constant when the sound pressure of the incident ultrasonic wave is small.

Expression (6) is an example of a time change function of the light intensity of the wedge luminous flux 9, and the same effect can be obtained as long as the light intensity is simply increased with respect to time. For example, consider a case where a light intensity function as shown in Equation (8) is given.

The calculation result in this case is shown in FIG. Although the amount of change in the light intensity of the diffraction image with respect to the depth d of the portion 71 of the light intensity of the diffraction image is larger than that in FIG. 12, the minimum value of the light intensity is about 18% of the maximum value, which is smaller than that in FIG. Thus, it can be confirmed that the light intensity function shown in the equation (8) is also effective.

The time Δt from entering the acoustooptic medium unit 2 until contacting the wedge light beam 9 may be approximately zero, or the distance from the acoustic aperture 203 to the irradiation region of the wedge light beam 9 may be acoustooptic. A value divided by the sound speed of the medium 201 may be used, or Δt obtained by actual measurement may be used. As an example of the actual measurement method, an ultrasonic wave is input from a sound source that is in close contact with the acoustic aperture 203, a dense wave is detected by a hydrophone installed in an irradiation area of the wedge luminous flux 9, and the ultrasonic input time and the dense wave are detected. A method of obtaining Δt from the time difference is conceivable.

From the above calculation, it was confirmed that by giving an arbitrary time change to the light intensity of the wedge luminous flux 9, a diffraction image having the same light intensity can be obtained regardless of the depth d of the portion 71 in the object 7. .

FIG. 14 schematically shows an example of an image photographed by the acousto-optic imaging device of the present embodiment. Since the exposure time of the imaging unit 4 is sufficiently longer than the repetition period of the trigger signal, diffraction images generated at different times within the exposure time are also exposed. Therefore, when a plurality of portions are located at different depths d as shown in FIG. 14A, they are projected onto the surface of the acoustic opening 203 of the ultrasonic wave as shown in FIG. 14B. A good image can be obtained. At this time, an image having the same luminance is obtained for each portion (A, B, C) regardless of the depth d.

As described above, according to the acoustooptic imaging device of the present embodiment, even when ultrasonic wave propagation attenuation occurs in an object, it is possible to obtain an image in which uneven luminance in a portion inside the object due to a position in the depth direction is suppressed. it can. In addition, since information inside the object is photographed as a two-dimensional or three-dimensional optical image using ultrasonic waves, the inside of the object can be photographed without using a signal processing circuit with high calculation processing capability. .

<Embodiment 2>
Hereinafter, a second embodiment of the acousto-optic imaging device of the present invention will be described. FIG. 15 is a schematic diagram showing the configuration of the acousto-optic imaging device 101 of the present invention.

(Configuration of acousto-optic imaging device 101)
The acousto-optic imaging device 101 is different from the first embodiment in that exposure is started at the timing of receiving the trigger signal every time the imaging unit 4 ′ receives the trigger signal from the trigger signal source 6.

FIG. 16 schematically shows the main components of the acoustooptic imaging device 101 and the signal flow thereof. The operation of the acousto-optic imaging device 101 will be described with reference to FIG.

First, the trigger signal generated by the trigger signal source 6 is input to the drive unit 51, the wedge light source 1, and the imaging unit 4 '. The drive unit 51 receives the trigger signal and generates a drive signal at the received timing. The ultrasonic source 5 receives a driving signal from the driving unit 51 and generates an ultrasonic wave corresponding to the driving signal. The generated ultrasonic wave enters the object 7, and the scattered ultrasonic wave generated by the object 7 enters the acoustooptic medium unit 2.

The wedge light source 1 receives the trigger signal and emits the wedge luminous flux 9 for a predetermined time T _w at the received timing. The light intensity of the wedge luminous flux 9 changes according to a predetermined light intensity function at a predetermined time T _{w based on} the input time of the trigger signal. Thereafter, the wedge light source 1 ends the output of the wedge luminous flux 9 and waits until the next trigger signal is input. A scattered ultrasonic wave and a wedge light beam 9 are incident on the acoustooptic medium unit 2 and come into contact with each other, whereby a diffraction image corresponding to the object 7 is generated.

The imaging unit 4 ′ starts exposure at the timing when the trigger signal is received, and ends the exposure after continuing the exposure for an arbitrary time. A diffraction image generated during exposure continuation is incident on the imaging unit 4 ′, and a diffraction image corresponding to the object 7 is acquired. In this manner, the acoustooptic imaging device 101 acquires an image of the object 7 via the ultrasonic wave 8.

As described above, the acousto-optic imaging device 101 according to the present embodiment is different from the first embodiment in that the imaging unit 4 ′ operates based on the trigger signal. Hereinafter, the operation of the acousto-optic imaging device 101 will be described in detail.

In the acousto-optic imaging device 101 according to the present embodiment, the imaging unit 4 ′ receives the trigger signal from the trigger signal source 6, starts exposure at the timing when the trigger signal is received, and performs exposure for a certain period of time. As the exposure duration _Te , a predetermined value may be used, or a value suitable for imaging an object may be input while the operator operates. When a predetermined value of the exposure duration T _e, for example imaging unit 4 'have a storage unit, it may be stored with exposure duration T _e in the storage unit, referenced at start of exposure May be. If the operator enters a value while operating, for example, the imaging unit 4 'have an input interface such as a keyboard and a potentiometer can enter the exposure duration T _e, the operator inputs the appropriate values during imaging The value may be referred to at the start of exposure.

Irradiation time T _w and exposure duration T _e of the wedge beam 9 is smaller than the repetition period Tt of the trigger signal. In the acousto-optic imaging device 101 of the present embodiment, exposure is performed every time a trigger signal is input and an ultrasonic wave is transmitted to obtain a diffraction image. Therefore, exposure is continued without reducing the repetition period T _t of the trigger signal. it is possible to increase the exposure amount per time T _e. Therefore, the repetition period T _t may be larger than the exposure duration T _e, for example, the exposure duration T _e is set sufficiently long, it is possible to obtain the perform still image only once.

FIG. 17 shows the operation timing of each part of the acousto-optic imaging device 101. FIGS. 17A to 17D show the same operation as in FIG. 11 up to the state where the trigger signal is input twice. FIG. 17E shows a state of whether or not the imaging unit 4 ′ is performing exposure. Here, exposure duration T _e is shorter than the irradiation time T _w of the wedge beam 9. In FIG. 17, the imaging unit 4 ′ starts exposure from the time t <b> 0 when the trigger signal is received, and exposes until the time when the dense wave 82 due to the scattered ultrasonic wave generated from the depth of d = 3 cm is in contact with the wedge light beam 9. exposure duration T _e of the imaging unit 4 'is set to continue. Since the exposure is completed at the time when the dense wave 82 due to scattered ultrasonic waves generated from the depth of d = 4 cm or more arrives, the diffraction image of the portion 71 having the depth of d = 4 cm or more is not captured. Thus, the acousto-optic imaging apparatus 101 according to this embodiment, by adjusting the exposure duration T _e, it is possible to adjust the depth direction of the depth of the region imaged (range).

18, the exposure duration T _e indicates the timing of the signals output from each part of the acousto-optic imaging apparatus 101 when longer than the irradiation time T _w of the wedge beam 9. Irradiation time T _w of the wedge beam 9, wedge light source 1 starts exposure time t0 that has received the trigger signal, the compression wave 82 due to scattering ultrasound resulting from the depth of d = 4 cm is in contact with the wedge beam 9 exposure duration T _e of the imaging unit 4 'is set to continue the exposure until after the time. At the time when the dense wave 82 by the scattered ultrasonic wave generated from the depth of d = 5 cm or more comes into contact with the wedge light beam 9, the imaging unit 4 ′ continues exposure, but the light intensity of the wedge light beam 9 is zero. Therefore, a diffraction image is not generated, and the portion 71 having a depth of d = 5 cm or more is not photographed. In this case, the depth in the depth direction of the area to be imaged is determined by the length of the irradiation time T _w of the wedge light beam 9.

17 and 18, for the sake of explanation, only the time waveform in which the dense wave 82 by the portion 71 located at every 1 cm depth from 1 cm to 5 cm is in contact with the wedge light flux 9 is shown. The dense wave 82 due to the portion 71 located at a depth of 1 mm is in contact with the wedge beam 9 at a time just between d = 1 cm and 2 cm. That is, the depth and the time during which the density wave 82 is in contact with the wedge light flux 9 change linearly. Therefore, in FIG. 17, the part 71 up to a depth of about 3.5 cm can be observed, and in FIG. 18, it can be said that the part 71 up to a depth of about 4.5 cm is observed.

According to the acoustooptic imaging device 101 of the present embodiment, an ultrasonic wave is input to the object 7 by inputting the trigger signal from the trigger signal source 6 not only to the wedge light source 1 and the drive unit 51 but also to the imaging unit 4 ′. Each time it is possible to acquire one image. At this time, by adjusting the shorter value of ones of irradiation time T _w of the exposure duration T _e or wedge beam 9 of the imaging unit 4 ', can be adjusted depth in the depth direction of the region imaged It becomes. Further, as in the first embodiment, an internal portion of an object photographed in one image is photographed with the same brightness regardless of the depth.

<Embodiment 3>
Hereinafter, a third embodiment of the acousto-optic imaging device 102 of the present invention will be described. FIG. 19 is a schematic configuration diagram of an acousto-optic imaging device 102 according to the third embodiment of the present invention.

(Configuration of acousto-optic imaging device 102)
The acousto-optic imaging device 102 is the second point that the imaging unit 4 ″ starts exposure after an arbitrary time delay after receiving the trigger signal, stops the exposure after continuing the exposure for an arbitrary time. Different from the embodiment.

FIG. 20 schematically shows the main components of the acousto-optic imaging device 102 and the signal flow thereof. The configuration of the imaging unit 4 '' and the operation of the acousto-optic imaging device will be schematically described with reference to FIG.

First, the trigger signal generated by the trigger signal source 6 is input to the drive unit 51, the wedge light source 1, and the imaging unit 4 ''. The drive unit 51 receives the trigger signal and generates a drive signal at the received timing. The ultrasonic source 5 receives a driving signal from the driving unit 51 and generates an ultrasonic wave corresponding to the driving signal. The generated ultrasonic wave enters the object 7, and the scattered ultrasonic wave generated by the object 7 enters the acoustooptic medium unit 2.

The wedge light source 1 receives the trigger signal and emits the wedge luminous flux 9 for a predetermined time T _w at the received timing. The light intensity of the wedge luminous flux 9 changes according to a predetermined light intensity function at a predetermined time T _{w based on} the input time of the trigger signal. Thereafter, the wedge light source 1 ends the output of the wedge luminous flux 9 and waits until the next trigger signal is input.

The scattered ultrasonic waves and the wedge light beam 9 are incident on the acoustooptic medium unit 2 and come into contact with each other, whereby a diffraction image corresponding to the object 7 is generated.

The imaging unit 4 '' includes an imaging element 4a and an exposure signal generation unit 4b. The exposure signal generator 4b receives the trigger signal, and generates an exposure signal after a predetermined time has elapsed from the received timing. The exposure signal generation unit 4b has a function of delaying the time for outputting the exposure signal by an arbitrary time with respect to the input time of the trigger signal. The exposure signal has a function of instructing the exposure time to the image sensor 4a. For example, the time during which the exposure signal continues may be the exposure time, and the exposure signal may include a signal indicating the exposure disclosure time and a signal indicating the exposure end time. The image sensor 4a receives the exposure signal from the exposure signal generation unit 4b, and ends the exposure after continuing the exposure for a predetermined time. When a diffraction image generated while exposure is continued enters the imaging unit 4 ″, a diffraction image corresponding to the object 7 is acquired. In this way, the acoustooptic imaging device 102 acquires an image of the object 7 via the ultrasonic wave 8.

The acousto-optic imaging device 102 of the present embodiment is different from the second embodiment in that the imaging unit 4 '' operates with a predetermined time delay from the trigger signal. Hereinafter, the acousto-optic imaging device 102 will be described in detail.

As described above, in the acousto-optic imaging device 102 of the present embodiment, the imaging unit 4 '' includes the imaging element 4a and the exposure signal generation unit 4b. The exposure signal generation unit 4b generates an exposure signal with a delay of an arbitrary delay time ΔTt from the time when the trigger signal is input from the trigger signal source 6. Exposure signal includes information time T _e of the imaging element 4a continues to exposure. Delay Delta] t _e and the exposure duration T _e may be using a pre-determined value may be input to the operator appropriate to the object imaging while the operation value. When a predetermined value of the exposure duration T _e, for example exposure signal generating section 4b have a storage unit, and stores the delay time in the storage unit Delta] t _e and the exposure duration T _e It may be referred to when generating an exposure signal. If the operator enters a value while operating, for example, the exposure signal generating section 4b have an input interface such as a keyboard and a potentiometer can enter the delay time Delta] t _e and the exposure duration T _e, when the operator imaging An appropriate value may be input and the value referred to at the start of exposure.

Imaging device 4a is delayed by the delay time Delta] t _e after the trigger signal is input to the imaging unit 4 '' and receives the exposure signal, the exposure is started. In addition, after the exposure by the time T _e, to end the exposure. Exposure duration T _e is less than the repetition period Tt of the trigger signal. Further, in the acoustic-optical imaging device 102, the total exposure duration T _e and the delay time Delta] t _e is preferably smaller than the irradiation time T _w of the wedge beam 9.

FIG. 21 shows the operation timing of each part of the acousto-optic imaging device 102 as in FIG. FIGS. 21A to 21D show the same operation as in FIG. 11 up to the state where the trigger signal is input twice. FIG. 21E shows a state of whether or not the imaging unit 4 '' is performing exposure. In Figure 21, the imaging unit 4 '' begins the exposure is delayed by a delay time Delta] t _e time t0 that has received the trigger signal, continues the exposure only during the time T _e. In FIG. 21, the exposure start time is earlier than the time when the dense wave 82 due to scattered ultrasonic waves generated from the depth of d = 2 cm contacts the wedge light beam 9, and the exposure end time is from the depth of d = 3 cm. It is set later than the time during which the dense wave 82 generated by the scattered ultrasonic waves contacts the wedge light beam 9. Since exposure is not performed during the time when the dense wave 82 arrives at a portion where d = 1 cm or less or d = 4 cm or more, a diffraction image of the portion 71 having a depth of d = 1 cm or less or d = 4 cm or more is not captured. Thus, in the acoustic-optical imaging device 102, the delay time Delta] t _e, of the depth direction of the range of an imageable region, by determining the end of the shallowest side, to adjust the exposure duration T _e, It is possible to adjust the range in the depth direction of the imageable region.

For the sake of explanation, FIG. 21 shows only a time waveform in which the dense wave 82 due to the portion 71 located at every 1 cm depth from 1 cm to 5 cm contacts the wedge light flux 9, for example, a depth of 1.5 cm The dense wave 82 due to the portion 71 located at is in contact with the wedge beam 9 at a time just between d = 1 cm and 2 cm. That is, the depth and the time during which the density wave 82 is in contact with the wedge light flux 9 change linearly. Therefore, in FIG. 21, it can be said that the portion 71 having a depth of about 1.5 cm to 3.5 cm can be observed.

The exposure duration T _e of the short to be to narrow the depth direction of the observation area, it is possible to obtain an image obtained by cutting out only the depth applicable. For example, as shown in FIG. 22A, when a plurality of portions are located at different locations in the depth direction of the object, the time at which the dense wave 82 by the portion indicated by B contacts the wedge light flux 9 is set as the trigger signal. a delay time Delta] t _e from start time, by setting a sufficiently short exposure duration T _e, as shown in FIG. 22 (b), to acquire an image of an internal body containing only a portion indicated by B it can. In this case, the resolution in the depth direction increases as the exposure duration time _Te decreases. However, the resolution cannot be increased more than the length of the ultrasonic wave 8 incident on the object 7. Therefore, the lower limit of the exposure duration T _e is approximately the duration of ultrasonic 8 (drive signals), it is possible to increase the resolution of the most depth in this case.

It is also possible to shoot the interior of the object at different delay time Delta] t _e. For example, the exposure duration T _e is set sufficiently short, as shown in FIG. 23 (e), (received a N-th trigger signal) N th trigger signal is generated based on the time t _N delay performing exposure by the imaging unit 4 '' in time Delta] t _eN and exposure duration T _e. Then, based on the (N + 1) th trigger signal to perform exposure by the imaging unit 4 '' in the delay time Delta] t _{eN + 1} and the exposure duration T _e. In this case, if the delay time Δt _{e + 1} is different from the delay time Δt _eN , the image acquired based on the (N + 1) th trigger signal is different from the image acquired based on the Nth trigger signal and the object 7. It can be obtained at the position. For example, by setting such a delay time Delta] t _{eN + 1} and the delay time Delta] t _eN differ by exposure duration T _e, the object inside, it is possible to acquire images at different adjacent depth positions. Thereby, images having different depths can be obtained for each frame. May be the delay time Delta] t _e different for each frame, may be varied delay time Delta] t _e after a few minutes imaging arbitrary frame at the same delay time Delta] t _e. By such a method, a plurality of tomographic images obtained by scanning an object perpendicular to the depth direction can be acquired. For example, as shown in FIG. 24 (a), by increasing the delay time Delta] t _e for each input of the trigger signal, when set to shoot at a deeper position, as shown in FIG. 24 (b), 1 frame Different tomographic images with different depths are obtained. Thus, in order to set the delay time Delta] t _e in accordance with the number of inputs of the trigger signal, for example, a storage unit provided in the exposure signal generating unit 4b of the imaging unit 4 '', as described above in the storage unit It is sufficient to incorporate a program for setting the image data and to operate the imaging unit 4 ″ with reference to the program in the storage unit.

Also, the storage unit of the imaging unit 4 '', the information of the pre-delay time Delta] t _e, if ask have a table that associates the depth d of the area to be imaged, a delay value of the time Delta] t _e at the time of imaging the aforementioned By referring to the table, it is also possible to obtain positional information of the acquired image depth.

When the exposure duration _Te is sufficiently short, the light intensity of the wedge luminous flux 9 does not necessarily change with time according to the light intensity function I (t) with reference to the time t _N when the trigger signal is generated. Also good. For example, as shown in FIG. 25A, the delay time Delta] t _e, when the exposure duration was T _e, with a light intensity of the wedge beam 9 function I (t) of Equation (6), I (Δt _It may be a constant value expressed by _e + T _e / 2). At this time, when changing the delay time Delta] t _e changes light intensity together. The timing for changing the light intensity may be the timing at which the trigger signal is input as shown in FIG. 25A (b), for example. In order to perform the control as shown in FIG. 25A (b), the wedge light source 1 has the light intensity function I (t) of the wedge luminous flux 9 in advance in the storage unit, and the delay time from the exposure signal of the imaging unit 4 ″. Referring to Delta] t _e and the exposure duration T _e, the calculation unit, the light intensity function I (t), and calculates the light intensity _{I (Δt e + T e /} 2) from the delay time Delta] t _e and the exposure duration T _e values The light intensity may be set to.

In FIG. 25A, the light intensity of the wedge light beam corresponding to the trigger signal generated at time t _{N + 1} is larger than the light intensity of the wedge light beam corresponding to the trigger signal generated at time t _N. This is at a time t _{N + 1} than the time t _N, because doing imaging in a deeper position. At time t time t _{N + 1} than _N, in the case of performing imaging at a shallower position, more of the light intensity of the wedge light flux corresponding to the trigger signal generated at time t _{N + 1} generates at time t _N It becomes smaller than the light intensity of the wedge luminous flux corresponding to the trigger signal. That is, the light intensity of the wedge light beam 9 corresponding to a plurality of trigger signals may increase or decrease with time.

Furthermore, as shown in FIG. 25B, the light intensity of the wedge luminous flux 9 may be constant. That is, the light intensity function I (t) may be constant regardless of the time t. In this case, since the ultrasonic wave is attenuated as the image is deeper, the luminance of the obtained image is smaller. However, since the duration time _Te is short, there is almost no difference in luminance caused by different positions in the depth direction in an image of one frame.

On the other hand, there may be a difference in the average brightness of the image between frames. For this reason, as shown in FIG. 19, the acousto-optic imaging device 102 may further include a signal processing unit 22 that receives an electrical signal from the imaging unit 4 ″ and adjusts the luminance of the captured image. The signal processing unit 22 includes one or both of at least two images so that the average luminance of at least two images among the images of a plurality of frames generated by the imaging unit 4 ″ repeatedly operating is constant. Adjust the brightness. More specifically, in two images acquired from two different depth positions of the object, the brightness of an image acquired from a relatively deep position is lower. Therefore, the signal is acquired so that the average luminance of the image acquired from the relatively deep position matches the average luminance of the image acquired from the relatively shallow position, or the average luminance difference between the two images is reduced. The processing unit 22 may adjust the brightness of images acquired from a relatively deep position or the brightness of two images.

In acousto-optical imaging apparatus 102 of the present embodiment, by adjusting the depth direction of the range of the area to be imaged by adjusting the delay time Delta] t _e and the exposure duration T _e. However, as shown in FIG. 26, when the exposure duration time _Te is longer than the irradiation time T _{w of} the wedge light beam, the same is achieved by adjusting the irradiation start time Δt _W of the wedge light beam 9 and the irradiation time T _w of the wedge light beam. It is also possible to obtain the effect. In this case, the delay time Delta] t _e may be zero or may be a value other than 0.

According to the acousto-optic imaging device 102 of this embodiment, the trigger signal from the trigger signal source 6 is input not only to the wedge light source 1 and the drive unit 51 but also to the imaging unit 4 ″, and exposure by the imaging unit 4 ″ is performed. by adjusting the timing and the exposure time delay Delta] t _e and the exposure duration T _e, it is possible to arbitrarily adjust the depth direction of the range of the area to be imaged. Further, by shortening the delay time Delta] t _e, it is possible to capture a tomographic image at any depth. By varying the delay time Delta] t _e depending on the number of acquisitions of the trigger signal, it is possible to obtain a tomographic image so as to scan the depth direction. It is also possible to associate the tomographic image to be acquired with the depth at which the tomographic image is located.

<Embodiment 4>
Hereinafter, a fourth embodiment of the acousto-optic imaging device of the present invention will be described. FIG. 27 is a schematic configuration diagram of an acousto-optic imaging device 103 according to the fourth embodiment of the present invention.

(Configuration of acousto-optic imaging device 103)
The acousto-optic imaging device 103 further includes a delay generator 19. The wedge light source 1 emits the wedge light beam 9 at the timing when the delay trigger signal is received by the delay trigger signal generated by the delay generator 19, and the driving unit 51. Differs from the second embodiment in that it transmits a drive signal.

FIG. 28 schematically shows the main components of the acoustooptic imaging device 103 and the signal flow thereof. The operation of the acousto-optic imaging device will be schematically described with reference to FIG.

First, the trigger signal generated by the trigger signal source 6 is input to the delay generator 19 and the imaging unit 4 '. The repetition period Tt of the trigger signal is preferably constant.

Delay generator 19 receives the trigger signal, with a delay from the timing with which the trigger signal is received by the time Delta] t _e, generates a delayed trigger signal. The delay generator 19 inputs the generated delay signal to the drive unit 51 and the wedge light source 1.

The drive unit 51 receives the delay trigger signal and generates a drive signal at the timing when the delay trigger signal is received. The drive signal generated by the drive unit 51 is input to the ultrasonic source 5.

The ultrasonic source 5 receives a drive signal from the drive unit 51 and generates an ultrasonic wave corresponding to the drive signal. The generated ultrasonic wave enters the object 7, and the scattered ultrasonic wave generated by the object 7 enters the acoustooptic medium unit 2.

Wedge light source 1 receives a trigger signal, at the received timing, emits a wedge beam 9 by a predetermined time T _w. Light intensity of the wedge beam 9, at a given time T _w relative to the input time of the trigger signal, varies in accordance with a predetermined light intensity function. Thereafter, the wedge light source 1 ends the output of the wedge luminous flux 9 and waits until the next trigger signal is input.

The scattered ultrasonic waves and the wedge light beam 9 are incident on the acoustooptic medium unit 2 and come into contact with each other, whereby a diffraction image corresponding to the object 7 is generated.

The imaging unit 4 ′ starts exposure at the timing when the trigger signal is received, and ends the exposure after continuing the exposure for an arbitrary time. A diffraction image generated during exposure continuation is incident on the imaging unit 4 ′, and a diffraction image corresponding to the object 7 is acquired. In this way, the acousto-optic imaging device 103 acquires an image of the object 7 via the ultrasonic wave 8.

Next, differences between the acousto-optic imaging device 103 and the second embodiment will be mainly described in detail.

(Delay generator 19)
In acousto-optical imaging apparatus 103 of the present embodiment, the delay generator 19 receives the trigger signal from the trigger signal source 6, a delay from the received timing by an arbitrary delay time Delta] t _e, generates a delayed trigger signal. Delay Delta] t _e may be using a pre-determined value may be input to the operator appropriate to the object imaging while the operation value. When a predetermined value of delay time Delta] t _e, for example the delay generator 19 have a storage unit, may be stored delay time Delta] t _e in the storage unit, referred to at the time delayed trigger signal generating You can do it. If the operator enters a value while operating, for example, delay generator 19 have an input interface such as a keyboard and a potentiometer can enter the delay time Delta] t _e, the operator inputs the appropriate values during imaging, The value may be referred to when generating the drive signal.

The delay generator 19 inputs the generated delay trigger signal to the drive unit 51 and the wedge light source 1.

(Driver 51)
The drive unit 51 receives the delay trigger signal and generates a drive signal at the received timing. Therefore, the driving signal is generated by a delay by the delay time Delta] t _e from the time of occurrence of the trigger signal.

(Wedge light source 1)
The wedge light source 1 receives the delay trigger signal and emits the wedge light beam 9 at the received timing. The light intensity of the wedge luminous flux 9 changes with time. Light intensity of the wedge beam 9, begins to change a delay by the delay time Delta] t _e from the time of occurrence of the trigger signal. The wedge light source 1 ends the output of the wedge luminous flux 9 after a time change according to a predetermined light intensity function for a certain time _Tw , and waits until the next trigger signal is input.

(Imaging unit 4 ')
Imaging unit 4 'starts exposure at the timing at which the trigger signal is received, perform exposure only exposure duration T _e. As the exposure duration _Te , a predetermined value may be used, or a value suitable for imaging an object may be input while the operator operates. When a predetermined value of the exposure duration T _e, for example imaging unit 4 'have a storage unit, it may be stored with exposure duration T _e in the storage unit, referenced at start of exposure You can do it. If the operator enters a value while operating, for example, the imaging unit 4 'have an input interface such as a keyboard and a potentiometer can enter the exposure duration T _e, the operator inputs the appropriate values during imaging The value may be referred to at the start of exposure. Exposure duration T _e is less than the repetition period Tt of the trigger signal.

FIG. 29 shows the operation timing of each part of the acousto-optic imaging device 103, as in FIG. 29A to 29D show the same operation as in FIG. 11 up to the state where the trigger signal is input twice. FIG. 29 (e) shows a state of whether or not the imaging unit 4 'is performing exposure.

As shown in FIG. 29B, the light intensity of the wedge luminous flux 9 changes with a predetermined light intensity function with reference to a time delayed by a delay time _ΔteN from the time t _N at which the trigger signal is received. As shown in FIG. 29C, the ultrasonic wave 8 is generated with a delay time _ΔteN from the time t _N at which the trigger signal is received, and is incident on the object 7.

The time for which the wedge light beam 9 is in contact with the dense wave 82 generated by reflection / scattering at the portion 71 in the object 7 varies depending on the time when the ultrasonic wave is incident and the depth d of the portion 71. In FIG. 29 (d), a sparse wave 82 generated by reflection / scattering of an ultrasonic wave that is input with a delay of _{Δte eN with} respect to the time t _N when the trigger signal is input is reflected by a portion 71 having a depth d = 1 cm. A state in which the wedge luminous flux 9 is contacted at time t _{N + 1} is shown. By adjusting the delay time _ΔteN , it is possible to change the depth d of the portion 71 where the dense wave 82 that contacts the wedge light beam 9 occurs at time _{tN + 1} .

Imaging unit 4 ', as shown in FIG. 29 (e), it continues only exposed for a time T _e from time t _N which has received the trigger signal. As shown in FIG. 29, a diffraction image of a portion 71 located at a depth of about 1.5 cm from approximately d = 1 cm to 2.5 cm is taken.

As described above, in the acousto-optic imaging device 103 according to the present embodiment, the delay time _ΔteN determines one end on the shallowest side in the depth direction of the _imageable region and adjusts the exposure duration _Te. Thus, the width in the depth direction of the imageable region can be adjusted.

Further, by shortening the exposure duration T _e By narrowing the photographing area in the depth direction, it is possible to obtain a tomographic image obtained by cutting out only the appropriate depth. For example, as shown in FIG. 22A, when a plurality of portions are located at different locations in the depth direction, the time when the dense wave 82 by the portion indicated by B contacts the wedge light flux 9 is the imaging unit 4 ′. object a start of exposure (t _N) later, so that the exposure duration T _e, including by adjusting the delay time Delta] t _eN, as shown in FIG. 22 (b), only the portion indicated by B in An internal image can be acquired. In this case, the resolution in the depth direction increases as the exposure duration time _Te decreases. However, the resolution cannot be increased more than the length of the ultrasonic wave 8 incident on the object 7. Therefore, the lower limit of the exposure duration T _e is approximately the duration of ultrasonic 8, it is possible to increase the resolution of the most depth in this case.

Further, the delay time _ΔteN may be varied. For example, set sufficiently short exposure duration T _e, as shown in FIG. 30, N-1 -th trigger signal delay time based on the time t _N-1 to generate a Delta] t _eN-1 and exposure duration T _{In step e} , exposure by the imaging unit 4 ′ is performed. Then, based on the N-th trigger signal to perform exposure by the imaging unit 4 'in the delay time Delta] t _eN and exposure duration T _e. In this case, if the delay time _ΔteN is different from the delay time _ΔteN-11 , the image acquired based on the (N + 1) th trigger signal is different from the image acquired based on the Nth trigger signal and the depth of the object 7. It can be obtained at the position. For example, by setting such a delay time Delta] t _eN and the delay time Delta] t _eN-1 differ by exposure duration T _e, the object inside, it is possible to acquire images at different adjacent depth positions. Thereby, images having different depths can be obtained for each frame.

May be the delay time Delta] t _e different for each frame, may be varied delay time Delta] t _e after a few minutes imaging arbitrary frame at the same delay time Delta] t _e. By such a method, a plurality of tomographic images obtained by scanning an object perpendicular to the depth direction can be acquired. For example, as shown in FIG. 25A, by increasing the delay time Delta] t _e for each input of the trigger signal, when set to shoot at a deeper position, as shown in FIG. 25B, the different depths for each frame A tomographic image is obtained. Thus, in order to set the delay time Delta] t _e in accordance with the number of inputs of the trigger signal, for example, a storage unit provided in the delay generator 19 incorporates a program for setting as described above in the storage unit The delay generator 19 may be operated with reference to a program stored in the storage unit.

Also, the storage unit of the delay generator 19, the pre-delay time Delta] t _e information and, if no table that associates the depth d of the area to be imaged, a delay value of the time Delta] t _e at the time of imaging the aforementioned By referring to the table, it is also possible to obtain positional information of the acquired image depth. According to the acousto-optic imaging apparatus 103 of the present embodiment, by adjusting the delay it is time to generate a delayed trigger signal time Delta] t _e and the exposure duration T _e, optionally in the depth direction of the range of the area to be imaged It becomes possible to adjust. Further, by shortening the exposure duration T _e, it is possible to capture a tomographic image at any depth. Further, by changing depending on the number of acquisitions of the trigger signal delay time Delta] t _e, it is possible to obtain a tomographic image so as to scan the depth direction. It is also possible to associate the tomographic image to be acquired with the depth at which the tomographic image is located.

When the exposure duration _Te is sufficiently short, the light intensity of the wedge luminous flux 9 does not necessarily change with time according to the light intensity function I (t) with reference to the time t _N when the trigger signal is generated. Also good. For example, a trigger period T _t, the delay time Delta] t _e, when the exposure duration was T _e, with a light intensity of the wedge beam 9 function I (t) of Equation (6), I _{(T t} + T _e / 2−Δt _e ). At this time, when changing the delay time Delta] t _e changes light intensity together. Repetition of such control to do is to have a light intensity function I (t) and the exposure duration T _e of the wedge light source 1 is previously wedge beam 9 in the storage unit, also a trigger signal from a signal of the delay generator 19 Referring to the period T _t and the delay time Delta] t _e, the calculating unit light intensity function I (t), repetition cycle T _t, the light intensity from the exposure duration T _e and the delay time Delta] t _e and the exposure duration T _e of the trigger signal The light intensity may be set to a value obtained by calculating I (T _t + T _e / 2−Δt _e ).

<Embodiment 5>
Hereinafter, a fifth embodiment of the acousto-optic imaging device of the present invention will be described. FIG. 31 is a schematic diagram showing the configuration of the acousto-optic imaging device 104 of the present embodiment.

(Configuration of acousto-optic imaging device 104)
The acousto-optic imaging device 104 includes the acousto-optic imaging devices of the first to fourth embodiments, an incident side mirror 20a, and an emission side mirror 20b. FIG. 31 shows an acoustooptic imaging device 104 including an incident side mirror 20a and an exit side mirror 20b in addition to the configuration of the acoustooptic imaging device of the first embodiment.

The wedge light beam 9 emitted from the wedge light source 1 is reflected by the incident side mirror 20a and enters the acoustooptic medium unit 2. The exit-side mirror 20b is disposed on the opposite side of the entrance-side mirror 20a with the acoustooptic medium unit 2 interposed therebetween, and the −1st order diffracted light beam 9a, the 0th order diffracted light beam 9b, and the +1 next time transmitted through the acoustooptic medium unit 2. The folded light beam 9c is reflected by the exit side mirror 20b and then enters the imaging optical system 3. The imaging unit 4 detects the diffracted light that has passed through the imaging optical system 3.

At the time of imaging, the ultrasonic source 5 is disposed in contact with the object 7 and outputs the ultrasonic wave 8 inside the object 7. The acoustooptic medium unit 2 is disposed in contact with the object 7 at the time of imaging, and takes in the scattered ultrasonic waves 8 a and 8 b generated in the object 7.

In the acousto-optic medium part 2, the wedge light beam 9 incident from the wedge light source 1 acts on the scattered ultrasonic waves 8a and 8b taken into the acousto-optic medium part 2, so that the −1st order diffracted light beam 9a and the 0th order diffracted light are obtained. A light beam 9b and a + 1st order diffracted light beam 9c are generated. The −1st order diffracted light beam 9a, the 0th order diffracted light beam 9b, and the + 1st order diffracted light beam 9c transmitted through the acoustooptic medium unit 2 enter the imaging optical system 3, and only the −1st order diffracted light beam 9a or the + 1st order diffracted light beam 9c. Enters the imaging unit 4.

According to the acousto-optic imaging device 104 according to the present embodiment, the wedge light beam 9 enters and exits the acousto-optic medium unit 2 via the incident-side mirror 20a and the exit-side mirror 20b. The system 3 and the imaging unit 4 can be arranged at a position other than a straight line across the acoustooptic medium unit 2. Therefore, the degree of freedom in optical design is increased, and a smaller image pickup apparatus can be provided.

The acousto-optic imaging device disclosed in the present application is useful as a probe for an ultrasonic diagnostic apparatus because it can acquire an ultrasonic image as an optical image. Moreover, since the ultrasonic wave radiated from the vibrating object can be observed as an optical image, it can be applied to uses such as a nondestructive vibration measuring apparatus.

1, 1 ′, 1 ″ wedge light source 2 acousto-optic medium unit 3 coupled lens system 3a second cylindrical lens 3b third cylindrical lens 4, 4 ′, 4 ″ imaging unit 5 ultrasonic source 51 drive unit 6 trigger Signal source 7 Object 7a, 7b Object 8 Ultrasonic wave 8a, 8b Scattered ultrasonic wave 81 Ultrasonic wave 82 Dense wave 9 Wedge light beam 9a -1st order diffracted light beam 9b 0th order diffracted light beam 9c + 1st order diffracted light beam 91 Monochromatic light beam 92 Plane wave light beam 10a Focal plane 10b Imaging plane

11 Laser light source 12 Magnifying optical system 13 Optical aperture 14 First cylindrical lens 15 Light intensity modulation signal source 16 Light modulator 17 Rotating disk 18 Photoelectric conversion element 19 Delay generator 20a Incident side mirror 20b Emission side mirror 21 Light shielding part

Claims (26)

1. A drive unit that generates a drive signal composed of burst waves by repetition of a plurality of reference waves;
   An ultrasonic source that receives the drive signal and outputs an ultrasonic wave corresponding to the drive signal to the inside of the object;
   An acousto-optic medium unit that has an acoustic aperture, and the scattered ultrasound generated by scattering of the ultrasonic wave inside the object enters and propagates from the acoustic aperture;
   A wedge light source that emits a wedge light beam that is incident on the acoustooptic medium portion non-parallel to the direction in which the scattered ultrasound propagates, and whose light intensity changes over time; and
   An imaging optical system in which the wedge light flux is diffracted in the acoustooptic medium part by the refractive index distribution generated in the acoustooptic medium part by propagation of the scattered ultrasonic wave, and the generated diffracted light is incident thereon, An imaging optical system that forms an image by focusing the diffracted light; and
   An imaging unit that captures an image formed by the imaging optical system and outputs an electrical signal;
   An acousto-optic imaging device.
2. A trigger signal source for generating a trigger signal;
   The acoustooptic imaging apparatus according to claim 1, wherein the driving unit receives the trigger signal and generates the driving signal at a timing when the trigger signal is received.
3. The wedge light source receives the trigger signal, and continuously emits the wedge light beam for a predetermined time at the timing when the trigger signal is received, and the light intensity of the wedge light beam increases within the predetermined time. The acousto-optic imaging device according to claim 2.
4. The acousto-optic imaging device according to claim 3, wherein the imaging unit receives the trigger signal, starts exposure at a timing when the trigger signal is received, continues exposure for an arbitrary time, and then stops exposure.
5. The acoustic imaging device according to claim 3, wherein the imaging unit receives the trigger signal, and after receiving the trigger signal, starts exposure with an arbitrary time delay, continues exposure for an arbitrary time, and then stops the exposure. Optical imaging device.
6. The trigger signal source repeatedly generates the trigger signal a plurality of times,
   The drive unit, the ultrasonic source, and the wedge light source each repeatedly operate each time the trigger signal is generated,
   Each time the imaging unit receives the trigger signal, after receiving the trigger signal, it starts exposure with an arbitrary time delay, continues exposure for an arbitrary time, then stops exposure,
   4. The light intensity of two wedge light beams corresponding to at least two of the plurality of trigger signals among the plurality of wedge light beams generated by the wedge light source repeatedly operating is different from each other. Acousto-optic imaging device.
7. A trigger signal source for generating a trigger signal; and
   A delay generator for receiving the trigger signal and generating a delayed trigger signal with a predetermined time delay;
   The wedge light source receives the delay trigger signal, and at the timing when the delay trigger signal is received, continuously emits the wedge light flux for a predetermined time,
   The drive unit receives the delayed trigger signal, generates the drive signal at the timing of receiving the trigger signal,
   
   The acoustooptic imaging apparatus according to claim 1, wherein the imaging unit receives the trigger signal, starts exposure at a timing when the trigger signal is received, continues exposure for an arbitrary time, and then stops exposure.
8. The acousto-optic imaging device according to any one of claims 4 to 7, wherein the imaging unit is configured to be able to change a time for which the exposure is continued.
9. A detector that detects a part of the wedge light flux that has passed through the acoustooptic medium portion and outputs a detection signal;
   The acousto-optic imaging device according to claim 2, wherein the trigger signal source generates a next trigger signal with reference to the detection signal.
10. The wedge light source is
    A laser light source that emits a monochromatic light beam;
    A magnifying optical system that emits a monochromatic light beam from the laser light source and emits an enlarged plane wave beam; and
    A cylindrical lens on which a plane wave light beam emitted from the magnification optical system is incident;
    Including
    The cylindrical lens has a refractive power for focusing in the first direction on a plane perpendicular to the propagation direction of the incident plane wave light beam, and has no refractive power in the second direction perpendicular to the first direction.
    The acoustooptic imaging apparatus according to any one of claims 1 to 9, wherein the first direction of the cylindrical lens is parallel to a direction in which the scattered ultrasonic wave propagates.
11. The wedge light source is
    A light intensity modulation signal source for generating a light intensity modulation signal;
    A laser diode that emits a light beam of the monochromatic light having a light intensity according to the light intensity modulation signal;
    The acousto-optic imaging device according to claim 10, comprising:
12. 11. The wedge light source further includes an optical modulator that modulates the light intensity of the monochromatic light beam emitted from the laser light source, the plane wave beam emitted from the magnifying optical system, or the plane wave beam emitted from the cylindrical lens. The acousto-optic imaging device described in 1.
13. The acousto-optic imaging device according to claim 12, wherein the optical modulator receives a modulation signal and modulates the light intensity of the monochromatic light beam or plane wave light beam in accordance with the modulation signal.
14. The light modulator is
    A rotating disk provided with a neutral density filter having a distribution in which the light attenuation rate differs in the circumferential direction;
    A motor for rotating the rotating disk,
    The rotating disk is arranged such that the monochromatic light beam or plane wave light beam passes through the neutral density filter,
    The acousto-optic according to claim 12, wherein the light intensity of the wedge light beam is changed by the attenuation factor of the light of the neutral density filter through which the monochromatic light beam or plane wave light beam is transmitted as the rotating disk rotates. Imaging device.
15. The acousto-optic imaging device according to any one of claims 1 to 5 and 7, wherein the temporal change in the light intensity of the wedge luminous flux is represented by a simple increase function.
16. The acousto-optic imaging device according to claim 15, wherein the simple increase function is an exponential function.
17. The acousto-optic imaging device according to claim 15, wherein the simple increase function is a power function or a function composed of a sum of power functions.
18. The acoustooptic imaging device according to any one of claims 1 to 17, wherein the number of reference waves in the burst wave is 10 or more and 1000 or less.
19. The trigger signal source repeatedly generates the trigger signal a plurality of times,
    The drive unit, the ultrasonic source, the wedge light source, and the imaging unit each operate repeatedly each time the trigger signal is generated,
    The predetermined time during which emission of the plurality of wedge light beams generated by the wedge light source repeatedly operating is different from each other in at least two of the plurality of wedge light beams. Acousto-optic imaging device.
20. The trigger signal source repeatedly generates the trigger signal a plurality of times,
    The drive unit, the ultrasonic source, the wedge light source, and the imaging unit each operate repeatedly each time the trigger signal is generated,
    The acoustooptic imaging apparatus according to any one of claims 4 to 7, wherein durations of exposure in a plurality of exposures caused by the operation of the imaging unit repeatedly differ from each other in at least two of the plurality of exposures.
21. The trigger signal source repeatedly generates the trigger signal a plurality of times,
    The drive unit, the ultrasonic source, the wedge light source, and the imaging unit each operate repeatedly each time the trigger signal is generated,
    The acousto-optic imaging according to claim 5, wherein a delay time until the start of exposure in a plurality of exposures due to repeated operation of the imaging unit is different from each other in at least two of the plurality of exposures. apparatus.
22. The trigger signal source repeatedly generates the trigger signal a plurality of times,
    The delay generator, the driving unit, the ultrasonic source, the wedge light source, and the imaging unit each operate repeatedly each time the trigger signal is generated,
    The acousto-optic according to claim 7, wherein the delay time until the start of signal output in the plurality of delay trigger signals generated by repeatedly operating the delay generator is different from each other in at least two of the plurality of delay trigger signals. Imaging device.
23. The acousto-optic imaging device according to claim 6 or 7, wherein a time for which the exposure in the imaging unit is continued is substantially equal to a time for which the burst wave of the driving signal is continued.
24. The wedge light source is based on a delay time until exposure starts in the exposure of the imaging unit and a time during which exposure continues, and light in the two wedge light fluxes corresponding to at least two of the plurality of trigger signals. The acousto-optic imaging device according to claim 6, wherein the intensity is determined.
25. An incident side mirror that reflects a wedge light beam emitted from the wedge light source and enters the acoustooptic medium unit;
    The acoustooptic imaging apparatus according to any one of claims 1 to 24, further comprising: an exit-side mirror that reflects the diffracted light generated in the acoustooptic medium unit and enters the imaging optical system.
    
26. A trigger signal source for generating a trigger signal; and
    A drive unit that receives the trigger signal and generates a drive signal composed of burst waves by repetition of a plurality of reference waves at the timing of receiving the trigger signal;
    An ultrasonic source that receives the drive signal and outputs an ultrasonic wave corresponding to the drive signal to the inside of the object;
    An acousto-optic medium unit that has an acoustic aperture, and the scattered ultrasound generated by scattering of the ultrasonic wave inside the object enters and propagates from the acoustic aperture;
    A wedge light source that emits a monochromatic wedge light beam incident on the acoustooptic medium portion non-parallel to the direction in which the scattered ultrasound propagates;
    An imaging optical system in which the wedge light flux is diffracted in the acoustooptic medium part by the refractive index distribution generated in the acoustooptic medium part by propagation of the scattered ultrasonic wave, and the generated diffracted light is incident thereon, An imaging optical system that forms an image by focusing the diffracted light; and
    An imaging unit that captures an image formed by the imaging optical system and outputs an electrical signal;
    A signal processing unit that receives the electrical signal from the imaging unit and adjusts brightness of the captured image;
    With
    The trigger signal source repeatedly generates the trigger signal a plurality of times,
    The drive unit, the ultrasonic source, the wedge light source, and the imaging unit each operate repeatedly each time the trigger signal is generated,
    The signal processing unit adjusts the brightness of at least two images so that an average brightness of at least two images is constant among a plurality of captured images generated by the operation of the imaging unit repeatedly. Acousto-optic imaging device.

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